230 OUR FORESTS AND WOODLANDS 
any unnecessary branches below 23 inches in dia- 
meter, and tarring the wound-surfaces, would be 
well spent in the improvement of the bole. 
Where grown in pure plantations, larch woods 
soon thin themselves and require underplanting. 
A pure larch wood of about thirty to forty years 
of age has only about half the density of a good 
crop of Scots pine, and even the latter cannot 
protect the soil for itself. Between the twentieth 
and thirtieth year the necessity for a free grow- 
ing-space makes itself unmistakably noticeable 
in larch plantations; and after that underplanting 
is essential, unless the soil is to be allowed to 
deteriorate and suffer gradual loss in capital value. 
There is of course always a great inducement 
to plant pure plantations of larch, as they soon 
yield thinnings of marketable value even in spite 
of the canker. And when the demand for such 
small poles is*good, as in hop-growing districts, 
pure crops can prove highly remunerative. The 
following example, furnished by an estate-agent on 
the Chiltern Hills, may show how profitable larch 
can be, even when grown on poor land, in southern 
England. ‘Larch plantations on the chalk sub- 
soil, overlaid with a good cap of flinty clay, 
